Flash ionization signatures in the type Ibn supernova SN 2019uo

TL;DR

This paper reports detailed observations of SN 2019uo, a type Ibn supernova with unique flash ionization features, rapid spectral evolution, and a bolometric light curve explained by nickel decay and circumstellar interaction.

Contribution

It presents the second known SN Ibn with flash ionization features and provides detailed spectral and photometric analysis of its unique properties.

Findings

SN 2019uo exhibits flash ionization features in early spectra.

It is fainter and has a different color evolution than typical SNe Ibn.

The bolometric light curve is well modeled by nickel decay plus circumstellar interaction.

Abstract

We present photometric and spectroscopic observations of the type Ibn supernova (SN) 2019uo, the second ever SN Ibn with flash ionization (He II, C III, N III) features in its early spectra. SN 2019uo displays a rapid post-peak luminosity decline of 0.1 mag d$^{-1}$ similar to most of the SNe Ibn, but is fainter ($M^V_{max} = -18.30 \pm 0.24$ mag) than a typical SN Ibn and shows a color evolution that places it between SNe Ib and the most extreme SNe Ibn. SN 2019uo shows P-cygni He I features in the early spectra which gradually evolves and becomes emission dominated post peak. It also shows faster evolution in line velocities as compared to most other members of the type Ibn subclass. The bolometric light curve is fairly described by a $^{56}$Ni + circumstellar interaction model.